The invention provides a heat insulation material for building. A synthetic resin foaming body (10) is placed in the center, wherein the synthetic resin foaming body (10) is formed by foaming after 60-75 wt% of low-density polyethylene (LDPE) resin, 7-13 wt% of flame retardant, 14-17 wt% of foaming agent, 0.3-0.6 wt% of stabilizer, 0.6-1.0 wt% of coupling agent and 0.8-1.2 wt% of surfactant are mixed; the synthetic resin foaming body (10) is connected with a glass fiber weaving plate (20) clamped between heat insulation foil on one side (21) and heat insulation foil on the other side (22) andadditional heat insulation foil (40) in a sticking mode. Therefore, after fusion of flame retardation of the synthetic resin foaming body (10) and flame retardation of the glass fiber weaving plate (20), it can be ensured that the flame-retarding effect is higher, and the heat insulation effect is achieved to the maximum.